I have read every post that I can find regarding solar charging for an RV. The amount of information out there is insane. Amp hours, PWN vs. MPPT, voltage loss, Amp storage etcÖ. I am overwhelmed at this point. I guess Iím just not very smart because I am at a loss. Someone please just tell me how many watts of solar panels to install on my trailer. I just want to keep my batteries charged without running my noisey generator. Here is the scenario:

We typically dry camp for two week spans. We have converted every bulb in the trailer over to LEDís. 2 standard group 24 12v batteries. We like to listen to the radio most days.We will watch an occasional movie. 12v TV/DVDIf it is cold we will run the furnace to take the chill off, not make it so hot you could bake cookies.The trailer has all the standard stuff that needs to be run.

In general what size panels do I need so I wonít have to run my generator? I will buy for x amount over just to be sure, but at this point I donít know where to start.Thanks

There are way too many variables and way too many unknowns to come up with an answer to your question. Not all solar panels are created equal, some are more efficient than others. Solar panels are relatively inefficient anyway. Will you be parked in the south or the north? Always in direct sunlight or not? Winter has less sunshine than summer so the answer will be different for each time of year. Are you going to be in Yuma that gets 340 days of sunshine per year or in Seattle which gets rain every other day? How often will you be crawling onto the roof to clean the dirt off the solar cells. The list of questions like this go on and on. The short answer is most RV roots aren't big enough to hold enough solar cells to make it so you never have to run the gen.

I have read every post that I can find regarding solar charging for an RV. The amount of information out there is insane. Amp hours, PWN vs. MPPT, voltage loss, Amp storage etcÖ. I am overwhelmed at this point. I guess Iím just not very smart because I am at a loss. Someone please just tell me how many watts of solar panels to install on my trailer. I just want to keep my batteries charged without running my noisey generator. Here is the scenario:

We typically dry camp for two week spans. We have converted every bulb in the trailer over to LEDís. 2 standard group 24 12v batteries. We like to listen to the radio most days.We will watch an occasional movie. 12v TV/DVDIf it is cold we will run the furnace to take the chill off, not make it so hot you could bake cookies.The trailer has all the standard stuff that needs to be run.

In general what size panels do I need so I wonít have to run my generator? I will buy for x amount over just to be sure, but at this point I donít know where to start.Thanks

This solar thing is never easy and it starts with what area of the country that you live in. Here in Sunny SoCal, I have 160W solar array and it does a nice job for me. We regularly camp for 10-days straight. Our batteries have never run down while camping. We've even had several days of partly cloudy........ the key is having a battery bank big enough to get you through the bad days and panels big enough to keep the batteries full by 2:PM on the good days.

2 weeks ago, we camped for 5 days at the beach. Woke up to leave at 5:AM on the 6th day and the battery voltage was 12.5V, after running the furnace all that night night (45* that night..... we leave our thermostat at 69*). BTW..... our panels are now 4-years-old.

I would recommend starting with either 2x 80W panels or 2x 100W and leave room for expansion That is buy a 20A controller.... it doesn't need to be an expensive MPPT controller with a small RV system. Also, use 8AWG wire from the panels to the controller and from the controller to the batteries.

That way you have room to expand your system by merely adding more solar panels, with no need to buy another controller or replace the wiring.

The other important item is be sure that you have approx 1 amp hour of battery storage for every watt of solar output. If you have 200W solar array, you will want a minimum of 200ah of batteries.

I installed my 160W system for under $500 (not including batteries) and the prices have since dropped. Today, you can get decent 80W solar panels for $140 each and a controller for $20........ wire, another $50-$60 (marine grade 8-2AWG wire). You don't have to buy exensive panels. The cost/reward factor is too great any more.

Fabricate some brackets to pop-rivet to the panels... bada-bing.... you have a system for around $350 + batteries..... if you find it inadequate (which I doubt from what you've said) add 2 more 80W panels for $280 (now your up to 320W) and you are still under $650.

The only thing that you do that we don't do is watch TV...... for that alone, I might suggest that you start with 3x 80W (240W). Even if you go with a 320W system, the 20A controller is just fine. Max output of 320W panels in perfect conditions (which is never) is 23A. The controller will handle that just fine. A friend of mine that camps with us regularly has that set-up. He even uses his microwave on the inverter but he also has a 450ah battery bank (4x 6V golf-cart batteries).

The big thing to understand is that you really can't do anything "Wrong" going with solar. Even if you just start with 1, 80W panel..... it will extend the length of time that you can go without charging the batteries. To ME... the key is starting with a minimum of a 20A controller and 8AWG wire. That way, expansion of your system is simple. Just keep adding more 80W panels (I just use 80W as an example) until you get it right.

The issue that you have is that you may want to replace those group 24 batteries with 2x 6V, deep cycle golf cart batteries at some point. That will be about $350 for decent ones.

The issue is, the solar panels work during the day when battery use is low. Battery use is highest at night, when there is no Sunlight. The batteries that you have will more than likely not get you through those partly cloudy to rainy days. However, that's something that you can face when the time comes. Replace the batteries with better ones when they need replacing.

Adding solar doesn't have to be complicated or painful. You really can't do anything wrong and as long as you stick with multiples of 80W or 100W panels, it's all good, no matter what. Just keep adding.

About the only recommendation I'd make is this.. IF you have the room, upgrade from a pair of G-24's in parallel (150 amp hours total far less usable) to a pair of GC-2 Golf car batteries in series (230 amp hours total and 115 usable) NOTE the total battery weight will increase. about 1/3 (Specifically by a ratio of 230/150) and the Golf Car batteries DO require maintenance.. Treat the two of them, in series, as though they were a SINGLE 12 volt battery.

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Nothing adds excitement like something that is none of your businessMy Home is where I park it.

Wavery - Thanks, very helpful. I live in San Diego so most of our camping is in the Southwest. Lots of Sun.

I have the rubber element roof, I can't remmeber the name EPMD (Sp). I know the tape is plenty strong, but what about the roof material pulling off of the wood? i don't want to drill holes but I'm a little concerned about the material pulling free. I even considered just having portable panels to avoid the mounting issue. What are you thoughts?

Wavery - Thanks, very helpful. I live in San Diego so most of our camping is in the Southwest. Lots of Sun.

I have the rubber element roof, I can't remmeber the name EPMD (Sp). I know the tape is plenty strong, but what about the roof material pulling off of the wood? i don't want to drill holes but I'm a little concerned about the material pulling free. I even considered just having portable panels to avoid the mounting issue. What are you thoughts?

Maybe someone else can answer the rubber roof question. I think, at the very least, I would glue down some wider, longer pads to attach the brackets too. There really isn't that much wind resistance to the solar panels. I highly doubt they would pull up the rubber roof but I really don't know.

If you kept the solar panels portable, you could get better efficiency out of them but I think that it would get old pretty quick. IMHO (after 30 almost years of solar experience) solar systems work best when you can set 'em and forget 'em. I don't even think about my battery power anymore. I just check the water in my batteries every couple months and that's it.

I bought my 1st 4, 80W solar panels for my yacht in 1985 for $600 each. I lived aboard and sailed around the world twice (14 years) with those solar panels. They went through 2 hurricanes (1 at sea) and many years in the tropical Sun. When I sold the boat in 2000, those panels were still going strong. The panels that I have now are stronger (frames), about the same size and output. Not a lot has changed in solar panel technology other than they are a whole lot cheaper now.

BTW..... we will be moving to our home in Fallbrook in September, so we will be neighbors....

Step 1: Add up your total amp hours needed dailyStep 2: Get batteries to support that that need times 2 for lead acid batteries. From your needs listed a pair of Trojan 105s might work. Both batteries equal 250 amp hours.Step 3: Install an inverter to support your needs something in 1000w to 2000w depending on your usage. Keep in mind you will not be able to run the AC and limited use of the microwave. Install the inverter as close to the batteries as possible, less then 3ft if possible with large enough wire.Step 4: Get 250 watts of solar panels. 2 x 125watt panels and the solar charger to go with it. There is a lot of debate over MPPT or not. For me the bottom line is the max input rate from the panels to the battery. 14.4 is too low 14.8 is ok 15v is best. Be sure to battery temperature compensate.

Step 1: Add up your total amp hours needed dailyStep 2: Get batteries to support that that need times 2 for lead acid batteries. From your needs listed a pair of Trojan 105s might work. Both batteries equal 250 amp hours. (they're actually 225ah)Step 3: Install an inverter to support your needs something in 1000w to 2000w depending on your usage. Keep in mind you will not be able to run the AC and limited use of the microwave. Install the inverter as close to the batteries as possible, less then 3ft if possible with large enough wire.Step 4: Get 250 amp hours of solar panels. 2 x 125watt panels and the solar charger to go with it. There is a lot of debate over MPPT or not. For me the bottom line is the max input rate from the panels to the battery. 14.4 is too low 14.8 is ok 15v is best. Be sure to battery temperature compensate.

I think that he meant, "Step 4: Get 250 amp hours of batteries. 2 x 125watt panels and the solar controller to go with it."

In my personal experience an inverter is not cost or power effective until one gets up into having a bank of batteries around 400ah (typically 4x 6V golf cart batteries or 2x 8Ds) and around 400W of solar panels.

110V through the inverter requires approx 10x the amperage draw as rated on the 110v appliance. In other words, a 1200W coffee pot is 10A @ 110V but its ~100A at 12V. It can be done with a 225A battery bank but a 15 minute pot of coffee will cost about 25ah. A 200W solar array will put out an average of about 60ah a day. I don't think that most people would want to dedicate 40% of their power consumption to 1 pot of coffee (for example).

However, the OP hasn't expressed the desire for 110V usage "YET"......... if that comes later, it's always doable.

As for MPPT controllers......... They are a must on a large system, like a home unit that has 20x 230W panels. In that case, a 10% improvement in power through a single controller makes financial, space and power sense. A 200W array is capable of putting ~90ah per day into the battery bank, an MPPT controller can add ~ 10% or 9ah per day. If it's a matter of spending $150 more on a good MPPT controller to gain 9ah or spending $150 to add an additional 100w solar panel that can add an additional 45ah prer day (5x the gain).... it's a no brainer, if you have the space for an additional solar panel.

Just reading the Costco magazine and on page E-6 a solar service is advertised... Grape Solar offering quotes for off grid battery systems for really good prices... might wanna check it out... Costco.com click on Grape Solar

Just reading the Costco magazine and on page E-6 a solar service is advertised... Grape Solar offering quotes for off grid battery systems for really good prices... might wanna check it out... Costco.com click on Grape Solar

They are a large outfit... the 5KW home grid tied option from CostCo is about $13,000 or $2.60/watt including all the mounting hardware, inverter, etc. That is a really good price. I expect that a RV system would cost even less per watt... with no inverter and less expensive roof mounting hardware.

If the eBay stuff doesn't work, try returning it... If the CostCo stuff doesn't work, return it, no problem. Up to you.

Wavery, Good practical and concise advice. I plan on adding Solar this Summer and I appreciate your insight. I also am in the area that you are moving to. I am going to spend the Summer at the Elks club in Oceanside.